The present invention relates generally to the microencapsulation of (4,5-dichloro-2-n-octyl-3(2H)-isothiazolone (DCOIT), a biocide product available from Rohm and Haas Company and analogues and derivatives thereof. Marine coating and paint manufacturers customarily add biocides to the paint to prevent or inhibit unwanted infestation of the films by microorganisms, e.g., fungi, such as molds and yeasts, and also by bacteria, algae, and cyanobacteria (so-called “soft fouling”) when these paints are applied on a vessel or underwater structure such as a pier. They have also been effective in some cases in preventing the growth of barnacles, tube worms, and the like (so-called “hard fouling”).
One biocide that has been investigated for use in marine paints and coatings to prevent or control soft fouling and hard fouling is DCOIT. However, the solubility of DCOIT is low in seawater and high in xylene. These properties have led paint manufacturers desiring to add DCOIT to marine paints to consider encapsulating DCOIT for incorporation into marine paints. DCOIT microcapsules are known in the art but the capsules reported in the literature to date have not been satisfactory. For example, xylene is a common solvent or base for marine paints. Unless the DCOIT capsules are essentially impermeable to xylene, the DCOIT may leak out of the capsules and react with the paint binders. This may cause viscosity increases in certain paint formulations or the DCOIT may cause undesirable plasticizing of the paint film. If the microcapsule is too permeable to water, the DCOIT may be leached away from the paint binder shortly after the paint film is applied rendering the paint vulnerable to attack by microorganisms at too early a stage in its service life. Accordingly, there is a need for improved encapsulated DCOIT compositions which provide in-can stability and yet gradually release the DCOIT in the marine environment.